Statistics encompasses scientific principles that must be considered not only after data collection, but throughout all processes, from the initial planning and implementation of a study to the analysis and interpretation of data. A researcher must also pay attention to the fundamental principles of statistics in selecting a sample, one of the first and most important steps in scientific research. Scientific research is a whole, and any principles neglected at any stage will lead to negative consequences in subsequent stages, undermining the scientific nature of the research.

One of the fundamental goals of scientific research, and therefore of the statistical research process, is to reach predictions and generalizations about the population (universe). Because reaching every individual within the population is costly, time-consuming, and sometimes impossible, subsets called samples must be taken to represent the population. For this sample to be representative of the population, both the method of determining the sample and the sample size must possess certain characteristics.

Qualitative research selects specific groups or individuals to obtain in-depth information, while quantitative research aims to create a large and representative sample to obtain generalizable results. However, both methods present certain challenges and limitations in sample selection. This study will focus on the problem of sample selection in surveys and scales, the most commonly used data collection methods in quantitative research, and will provide information on determining sample size.